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Date: Mon, 27 May 2013 15:10:04 +0200
From: Michael Gronager <gronager@ceptacle.com>
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Subject: Re: [Bitcoin-development] BIP0032
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Commenting on my own mail...

Rereading the BIP, it occurs to me that the private derivation is
actually intentional. So:
(m/i/j/k)*G = (M/i/j/k), but (m/i'/j/k)*G <> (M/i/j/k) (M/i'/j/k => ERROR)

But: ((m/i')*G)/j/k = (m/i'/j/k)*G

So, the motivation for the private derivation is to avoid the known (K,
c) and known k_i => k known too! I fear that many will fall in this
trap, though...

/Michael